Fan blade



Aprii 20, 1937. M sMn-H, JR 2,077,959

FAN BLADE Filed Aug. 16, 1935 3 Sheets-Sheet l INVENTOR. Mew/1m 4 5mm,Jr

ATTORNEY April 20, 1937. M. A. SMITH, JR

FAN BLADE Filed Aug. 16, 1935 3 Sheets-Sheet 2 III/ll IN VEN TOR.Mira/14114 JM/m, Je BY f g ATTORNEY.

April 20, 1937. M. A. SMITH, JR

FAN BLADE Filed Aug. 16, 1935 I5 Sheets-Sheet 3 IN V EN TOR. MI/JJHHLLFl. 5mm, J2 BY M A TTORNEY Patented pr. 20, 1937 PATENT Marshall A. SmitJr., South Bend, Ind, as-

signor to Bendix Products Corporation, South Bend, Ind., a corporationof Indiana Application August 16, 1935', Serial No. 36,468 2 Claims.(or. 170-159 This invention relates to ventilating fans of the typeintended for use where the blades of a fan are subjected to severeabrasive or corrosive o in unevenness of operation and distortion of theentire structure.

It is therefore an object of this invention to provide a ventilating fanwherein the blades and hub of the fan are provided with a protectivecovering of rubber Or other corrosive-resistant material.

Another object of the invention lies in the provision of a process bywhich a thin coating of corrosive-resistant material can be fastened toa fan blade by means of a process similar to the process by whichcertain metals are electroplated on other materials.

A still further object of the invention is to provide means whereby athin coating of corrosive and abrasive resistant material can besecurely attached to the blades and hub of a fan in such a manner thatthe coating material will become an integral part of the structure,thereby resisting the forces tending to remove the protective covering.

A further object of the invention is to provide a fan blade wherein aperforated core member of metal or other suitable material is employedto shape the blade structure, and a thin layer of insulating material iselectroplated on the core member in such a manner that the insulatingmaterial flows through the coremember to form insulating rivetsextending through the core member to tie the insulating materialsecurely to the fan blades on opposite sides thereof.

Another object of the invention is to provide a moulded fan bladewherein a small core member conforming to the shape of the finished fanblade, or formed of a metal stamping of any desired shape may beemployed to reinforce the structure of 'the moulded fan blade.

A still further object of the invention is to provide a reinforced fanblade, wherein tension members such as strands of wire are moulded inthe fan blade to absorb the centrifugal and torsional forces to whichthe fan blade is subjected;

Other desirable features and combinations of this invention relate toforming longitudinally and transversely extending grooves in the surcoremember to securely tie the rial to the fan blade on opposite sidesthereof;

face of the core of the fan blade to-aid in securing the insulatingmaterial to the fan; forming a plurality of apertures through the coremember to which the insulating material is secured to form insulatingrivets extending through the insulating mateand'to provide an insulatedfan blade wherein the skin friction of the blade is minimized.

Other objects and advantages of this invention will be apparent from thefollowing detailed description, considered in connection with theaccompanying drawings, submitted for purposes of illustration only andnot intended to define the scope of the invention, reference being hadfor that purpose to the s bjoined claims:

In the drawings, wherein similar reference characters refer to similarparts throughout the several views:

Figure 1 is a plan the construction of partly in section showing theblade;

Figure 2 is a view Figure 1;

Figure 3 is Figure 1;

Figure 4 is a view of a portion of a fan blade, showing a modified formof the method of securing the insulating material to the fan blade;

Figure'5 is a cross section on the'line 5-5 of Figure 4, showing onedesirable manner of securing the insulating material to the metal coreof the fan blades;

Figure 6 is a view similar to Figure 5 showing a modified form;

Figure '7 is a view similar to Figure 4 showing a moulded fan blade,wherein a small apertured metal core is employed;

Figure 8 is a view taken on the line 8-8 of Figure "I;

Figure 9 is a view similar 'to Figure 7, wherein an apertured metalstamping is employed as a rigidifying core;

Figure 10 is a view taken on the line Ill-l0 of Figure 9;

Figure 11 is a view similar to Figure 9, showing a moulded. fan bladewherein a core member of drawn wire, or other suitable material isemployed; and

taken on the line 2-2 of a view taken on the line 3-3 of Figure 11.-

Referring more particularly to Figure 1, there is shown a fan blade ofthe general type disclosed in my copending application Serial No. 5,691,filed February 9, 1935. In this embodi-,

. ment of the invention there is shown a fan blade having a hub sectionI0, and a. bladed section E2. The illustrated blade is of the constantvelocity type wherein a uniform quantity of air 5 is delivered over theentire working area of the fan blade. It will be understood, however,that this invention may be applied to other types of fan blades than theone illustrated. As shown the fan blade 82 is provided with a pluralityof- -10 apertures M, extending through the blade section.

In the preferred embodiment of the invention a thin layer of colloidalsolution of latex I6 is fixed to the outer surface of the core and hub15 structure by means of a process similar to the process wherebycertain metals are electroplated on the surface of other metals. Toprepare the structure for latex electroplating process the hub and coresof the blades of the fan are assembled. The structure is thensand-blasted to remove all foreign matter from the surface of the core,and to roughen the surface of the cores and hub so that theelectroplated solution may more securely grip and fuse with the coremember to form 25 an integral structure. After the structure has beensand-blasted it is placed in a drier, wherein it is subjected to atemperature of a suitable degree such as from 185 to 190 Fahrenheit fora suitable period to adequately dry the structure 30 preparatory to thenext operation. It has been found from experiment that approximately twohours is adequate to properly prepare the structure for theelectroplating operation.

7 After the structure has been thus suitably pre- 35 pared, it is placedin an electroplating tank, wherein a solution of a suitable consistencyof a colloidal solution of latex is transferred from the negative orcathode terminal to the positive 1 or anode terminal.- It will be notedthat inelec- 40 troplating rubber, the article to be plated ispositioned on the positive or anode terminal, whereas in electroplatingmetal, the article to be plated is positioned on the negative or cathodeterminal. The structure to be treated is subjected to the 45electroplating process for a period of time dependent upon the desiredthickness of the .protective covering. It has been found from experimentthat approximately of an inch of latex will be deposited upon thestructure in approximately thirty minutes. The length of time duringwhich the structure is subjected to the electroplating bath is thereforeentirely 7 de-' pendent upon the desired thickness of the insu- 55lating material.

After the desired thickness of insulating material has been deposited,the structure is removed from the electroplating bath, and is subjectedto a steam vulcanizing process wherein 60 the structure is subjected toboth pressure and temperature to dry the colloidal solution of latex,and to harden it to the desired degree. It has been found fromexperiment that a temperature of approximately 375 Fahrenheit, and apres- 65 sure of approximately 165 pounds will harden thecolloida'lsolution of latex to a proper degree for certain types ofworkin approximately six to eight hours.

After the structure has been vulcanized it is 7 removed from thevulcanizer, and is subjected to a bufiing and polishing operation. Asoft bufier or polisher is employed, and after the structure has beensuitably polished it is'waxed to decrease the skin friction of theblades and hub. 75 Ithas been found that a fan blade prepared tendthrough the blade section.

in accordance with the process indicated above will possess a skinfriction approximating that of the best metal blade structure now inuse.

One of the greatest difficulties encountered in electroplatinginsulating material on fan blades 5 is to secure the insulating materialto the fan blades in such a manner that centrifugal and torsional forceswill not cause it to crack or slip on the fan blades. The upper surfaceof the blade as viewed in Figure 2 is subjected to the 10 greateststress because of the fact that the upper surface of the blades issubjected to negative pressure developed in the normal operation of thefan. The lower surface of the blades of the fan is subjected to pressurewhich tends to urge the covering material l6 toward the blades l2. Inthe embodiment of the invention illustrated in Figures 1 and 2 aplurality of apertures M ex- When the insulating material I6 iselectroplated on the blade structure it flows through the apertures M toform, in effect, rubber rivets i8 joining the in sulating material I6 onopposite sides to the blade section #0.

Other expedients may be resorted to to securely tie the insulatingmaterial l6 to the core member E2 of the blades. Figures 4 to 6illustrate other desirable embodiments wherein longitudinally extendinggrooves or slots 29 are formed in the surface of blade structure l2 sothat the electro- 30 plated material may flow into the grooves tosecurely lock the insulating material to the blades. Transverselyextending grooves 22 may also be positioned in the blades to relieveagainst centrifugal forces to which the blade is subjected. 30

In the embodiment illustrated in Figure 5, it will be observed that thelongitudinally extending grooves 20 are tapered, pointing toward thetrailing edge of the blade, and that the transversely extending groovesare also tapered and are pointed toward the outer end of the bladesection. This disposition of the grooves tends to cause the insulatingmaterial E6 to cling more tightly to the core member it to thecentrifugal, torsional and frictional forces acting on the blade duringnormal operation thereof.

In the embodiment of Figure 6, the grooves 2| are formeddn theshape ofways which cause the insulating material 16 to become securely locked inthe core member i2.

The embodiment of the invention illustrated in Figures '7 and 8 shows amoulded blade structure wherein a small rigidifying core 30 of airfoilcross section is employed to stiffen and strengthen the blades. Inthisembodiment of the invention, a moulded blade structure of acomposition of rubber or other suitable material is provided. The

- blade structure is formed with a suitable airfoil shaped core memberhaving apertures formed therein to permit the moulded material to flowthrough the core member, thereby forming insulating rivets extendingthrough the 'core structure to securely tie the insulating materialtogether on opposite sides of the core member. In this embodiment of theinvention an insulating material of suitable consistency is moulded uponthe core member at a temperature and pressilre'to produce a bladestructure of the proper hardness consistent with the requirements of thefinished product. After the structure has been moulded it is removedfrom the mould and subjected to a polishing and waxing operation toobtain the desired friction coefiicient.

In the embodiment illustrated in Figures 9 and 10, a core member 40formed of a metal stamping or other suitable material is positioned inthe mould. It will be observed that in this design it is not necessarythat the core member to conform to the airfoil section of the finishedproduct. In this embodiment of the invention apertures 52 extend throughthe core member it to securely tie the insulating material together onopposite sides of the core member. Insulating material 46 of rubber orother suitable composi tion is moulded around the core member M in amanner similar to that discussed in connection with the embodimentillustrated'in Figures 7 and 8.

In the embodiment illustrated in Figures 11 and 12, the core structurecomprises several strands of drawn wire 50 interposed within the mouldedmaterial 52 of the fan blade. The core structure may extend through bothblades of the fan, passing around the hub structure to securely tie theblades together, and to aid in ab-' sorbing centrifugal and other forcesto which the blades are subjected during normal operation. In theembodiments of the invention illustrated in Figures '7 to 12, themoulded material may be moulded to the core member direct. In order tosecure a more perfect bond between the insulating material and the coremember, however, I prefer to electroplate a thin coating of insulatingmaterial to the core member before it is subjected to the mouldingoperation. a

It will be observed that this invention provides a fan blade whereininsulating material is securely fixed to or formed integral with thecore structure, to form a fan structure adapted to resist corrosiveaction, and to minimize abrasion, where the fan is employed inindustrial or chemical plants, or in places where dust or grit is mixedwith the air driven by the fan, which would impede the operation of thefan, and injure a conventional metal fan.

While the invention has been described with particular reference tocertain preferred embodiments thereof, it is understood that the scopeof the invention is not limited to the details illustrated and describednor otherwise than by the terms of the following claims.

I claim:

1. A metal fan blade having a plurality of longitudinally andtransversely extending undercut grooves formed in the surface of themetal blade, the pointed ends of the grooves project-' ing toward thetrailing and tip ends of the blade respectively, a protective coveringof a colloidal solution of latex electroplated on the metal blade andengaging in the grooves to securely tie the protective covering to theblade and to cause it to cling more tightly thereto during normaloperation of the fan when the blade is subjected to centrifugal,torsional and frictional forces.

2. A metal fan blade having a plurality of Iongitudinally extendingundercut grooves formed in the surface of the metal blade, the pointedends of the grooves projecting toward the trailing edge of the blade, aprotective covering of a colloidal solution of latex electroplated onthe metal blade and engaging the grooves to securely lock the protectivecovering to the blade and to cause it to cling thereto during normaloperation of the fan when the blade is subjected to centrifugal,torsional and frictional forces.

MARSHALL A. SMITH, JR.

